feat: add $schema to config examples

config_examples/config_binance.example.json

@@ -1,4 +1,5 @@
 {
+    "$schema": "https://schema.freqtrade.io/schema.json",
     "max_open_trades": 3,
     "stake_currency": "USDT",
     "stake_amount": 0.05,

config_examples/config_freqai.example.json

@@ -1,4 +1,5 @@
 {
+    "$schema": "https://schema.freqtrade.io/schema.json",
     "trading_mode": "futures",
     "margin_mode": "isolated",
     "max_open_trades": 5,

config_examples/config_full.example.json

@@ -1,4 +1,5 @@
 {
+    "$schema": "https://schema.freqtrade.io/schema.json",
     "max_open_trades": 3,
     "stake_currency": "BTC",
     "stake_amount": 0.05,

config_examples/config_kraken.example.json

@@ -1,4 +1,5 @@
 {
+    "$schema": "https://schema.freqtrade.io/schema.json",
     "max_open_trades": 5,
     "stake_currency": "EUR",
     "stake_amount": 10,

freqtrade/templates/base_config.json.j2

@@ -6,6 +6,7 @@
             "refresh_period": 1800
         }' %}
 {
+    "$schema": "https://schema.freqtrade.io/schema.json",
     "max_open_trades": {{ max_open_trades }},
     "stake_currency": "{{ stake_currency }}",
     "stake_amount": {{ stake_amount }},